(1) Field of the Invention
The present invention relates to a membrane with bumps for testing a fine electrical circuit formed on a semiconductor wafer, a liquid crystal display panel, a solar battery, or the like by causing the bumps to have surface contact with contacting parts of the fine electrical circuit so as to have plural electrical contacts simultaneously, as well as relating to a method of manufacturing a probe card including such membrane with bumps, and the like.
(2) Description of the Related Art
In recent years, there has been an active effort underway to achieve higher accuracy and higher speed, as well as larger semiconductor devices in order to provide more sophisticated semiconductor devices, or the like and to reduce costs. For example, there has been an ongoing effort to achieve a finer patterning of electrical circuits formed on a semiconductor wafer as well as a larger wafer of a semiconductor wafer. Therefore, for a test of operation of an electrical circuit, pitch intervals between contacting parts are required to be smaller and thus a number of electrical contacts to be provided simultaneously is required to be larger.
The following describes a conventional method of manufacturing a probe card (for example, refer to Japanese Laid-Open Patent application No. 08-235935).
Referring to FIG. 1, a through-hole 1102 is formed in a polyimide film 1101. Then, such through-hole 1102 is filled with a metal substance, so that a rivet-shaped metal projection 1104 is formed, with the rivet-shaped metal projection 1104 including swollen portions 1103, on both surfaces of the above-mentioned film, whose diameters are larger than a diameter of the through-hole 1102. A shape of this rivet-shaped convex electrode 1104 is a typical shape of electrodes formed by a metal plating method, as disclosed in Japanese Patent No. 3098130 (hereinafter referred to as Patent Document 2).
However, since such rivet-shaped convex electrode 1104 is formed by a metal plating method, it is difficult to control its shape. It is extremely difficult to control a size of diameters of the swollen portions 1103 since their diameters are greatly affected by various factors such as accuracy of forming a hole in the polyimide film 1101, a shape and surface roughness of such hole, as well as a chamfered shape.
A result of an evaluation conducted by the inventor of the present invention (hereinafter simply referred to as “the present inventor”) shows that, when one-thousand rivet-shaped convex electrodes 1104 whose swollen portions are 100 μm in diameter were formed, diameters of these resulting swollen portions were in a range φ100±10 μm, and thus that it was difficult to have equal and normal electrical contacts by all electrodes. In a case where the number of convex electrodes is increased, it is possible that there will be increased variations in shape of their swollen portions.
Meanwhile, in a case where a rivet-shaped convex electrode 1104 is formed by a plating method, its swollen portion does not have a beautiful semispherical shape but a squashed shape as shown in FIG. 2.
A probe card is used to have plural electrical contacts simultaneously by causing convex electrodes 1104 and contacting parts of an electrical circuit to have surface contact. Thus, in a case where diameters of the convex electrodes 1104 are not uniform and do not have a beautiful semispherical shape, the following problems occur: a size of contacting parts to come in contact with such convex electrodes 1104 are required to be larger than necessary, which results in a defect in a case of a fine electrical circuit; and a predetermined electrical contact cannot be assured unless a greater pressing force is applied.
Furthermore, since it is difficult to control the swollen portions 1103, which are grown by performance of natural plating growth, there is also a serious problem in that many defects occur and thus costs for probe cards increase due to lowered yields.
The following describes a method of manufacturing a probe card according to a second conventional technology (for example, refer to Patent Document 2).
The method disclosed in this Patent Document 2 is a solution to problems of technology disclosed in Patent Document 1. Referring to FIG. 3, an anisotropic conductive film 1302 is added between convex electrodes 1104 and a wiring circuit 1303 in order to assure electrical continuity by absorbing variations in a height of the convex electrodes 1104 caused by non-uniform diameters of the convex electrodes 1104, which is a problem in Patent Document 1. With this structure, each electric signal generated by an electrical circuit 1301 to be tested is independently transmitted to the wiring circuit 1303 via a pressed portion formed by the convex electrode 1104 pressing a portion of the anisotropic conductive film 1302.
However, since this method uses the anisotropic conductive film 1302, which is relatively expensive, there is a problem of an increased cost and a shortened useful lifetime due to deterioration of the anisotropic conductive film 1302. More specifically, the anisotropic conductive film 1302 is made of elastic film in which conductive particles are arranged, and by being pressed to a certain degree, conductive particles in such pressed portion adhere to one another to allow electricity to flow. However, in a case where an operational test of the electrical circuit 1301 is conducted under temperatures in a range between 20° C. and at least 100° C., the elastic film expands and contracts greatly in a planar direction of the film due to thermal expansion. Furthermore, the above test is conducted, in general, for plural times by exchanging test subjects, and the elastic film is pressed with a certain degree of force every time a test is conducted, as is disclosed in Patent Document 2. Under these circumstances, electrical resistance values of the conductive particles included in the anisotropic conductive film 1302 vary with time since a shape of the elastic film constantly changes by being pressed, although such electrical resistance values are stable when the conductive particles are in an original arrangement. In other words, since the original arrangement of the conductive particles changes due to distortion caused by thermal expansion and contract and distortion caused by a repeatedly applied load, their electric resistance values become unstable.
A result of an evaluation conducted by the present inventor shows that, the electric resistance values of contacting parts of the anisotropic conductive film 1302 tend to be greater after the operational test of the electrical circuit 1301 is conducted several hundred times, and thus that stable test results cannot be achieved.